In U.S. Pat. No. 4,690,912, Paulik et al. disclose a bromide- or iodide-promoted rhodium catalyst system for the carbonylation of carbonylatable reactants. In Example 55, butadiene is converted to greater than 79 wt. % C.sub.5 carboxylic acids.
In U.S. Pat. No. 4,622,423, Burke discloses the preparation of 3-pentenoic acid by hydrocarboxylating butadiene with carbon monoxide and water in the presence of a rhodium-containing catalyst, an iodide promoter and certain halocarbon solvents. Methylene chloride is the preferred solvent; acetic acid in aqueous solution is said to be undesirable.
In U.S. Pat. No. 4,788,334, Burke discloses a process for the hydrocarboxylation of linear olefinically unsaturated esters and terminally unsaturated alkenes having 4 to 16 carbon atoms to form a mixture which contains an increased amount of the linear carboxylic acid. The reaction mixture comprises the ester or the terminally unsaturated alkene, carbon monoxide, water, a halocarbon or aromatic solvent, a rhodium catalyst, an iodide promoter and a mildly acidic accelerator.
In U.S. Pat. No. 3,816,488, Craddock et al. disclose an improved process for the production of carboxylic acids by the reaction of ethylenically unsaturated compounds with carbon monoxide and water, in the presence of catalyst compositions essentially comprising rhodium compounds and complexes, together with an iodide promoter in critical proportions (I:Rh=3:1 to 200:1) to obtain predominantly linear products.
In U.S. Pat. No. 5,145,995, Burke discloses a process for the preparation of 3-pentenoic acid which comprises reacting in a solvent consisting essentially of at least one carboxylic acid selected from the group of aliphatic C.sub.2 -C.sub.20 carboxylic acids, benzoic acid and alkyl-substituted benzoic acids wherein the total number of carbons in the alkyl group(s) is not more than 3: butadiene, carbon monoxide, and water with a rhodium catalyst and a promoter selected from the class consisting of bromide and iodide.
In U.S. Pat. No. 4,645,863, Rebafka et al. disclose a process for the preparation of unsaturated alcohols and/or esters thereof by reacting conjugated dienes with water and/or aqueous lower aliphatic carboxylic acid solutions in the presence of a macroporous acid ion exchanger having an average pore diameter greater than 50 Angstroms, and a polar aprotic solvent.